Plant Kingdom

• Cyanobacteria are also called the prokaryotic algae.

• Due to prokaryotic nature, classified under kingdom Monera.

• Aniso means dissimilar,

• Hence, when two dissimilar sized gamete fuses it is called anisogamy.

• In members of Phaeophyceae, the plant body is attached to the substratum by holdfast, has a stalk, the stipe and leaf like photosynthetic organ, the frond.

• Gametophytic phase is the dominant phase of life in bryophytes, hence dominant phase is haploid.

• It lacks true root, instead of that rhizoids are present.

• All the other three options have true roots, however, pteridophytes are also water dependent.

• Prothallus is a small, multicellular, free living and photosynthetic thallus.

• Formed by the germination of meiospores produced inside the sporangium.

• In gymnosperms the sporophylls cluster together form a compact structure called the cone; which is the salient feature of this division.

• Main plant body is sporophyte [2n].

• It shows xerophytic adaptations, helps to resist extreme conditions which are:

Thick cuticle, needle shaped leaf, sunken stomata and sclerenchymatous hypodermis. All these adaptation helps to minimise water loss through transpiration.

In the embryo sac of angiosperm 3 antipodal cells, 2 synergid, one egg cell and a secondary nucleus is present. All of them contains one nuclei except the polar cell in which 2 nucleus are present

Endosperm is triploid [3n] in angiosperm. As 2n=36, n=18

Hence chromosome number in endosperm,3n= 3*18

=54

Due to fusion of a male gamete[n] with secondary nucleus [2n], triploid [3n] PEN(primary endosperm nucleus) is formed.

Protonemma represents either a filamentous or a globose gametophytic structure which is formed by the germination of haploid spores.

• Sequoia is a plant in which ovule is naked and no fruit formation takes place.

• It is the tallest tree.

Mannitol is the reserve food material of Phaeophyceae, the brown algae.

A. Volvox

B.Pinus

C. Ectocarpus

Rhizoids, these are the thread like structures. In liverworts unicellular rhizoids are present and in mosses multicellular rhizoid with oblique septa are present.

A. Ectocarpus

B. Fucus

A) antheridium and B) archegonium

Bryophytes are called the amphibians of plant kingdom due to following reasons:

a) They inhabit two well defined habitats i.e. land and water.

b) Bryophytes can complete their life cycle without water; water is required for fertilisation,

c) Water also plays an important role in dehiscence of antheridium and archegonium.

d) As it lacks proper vasculature, water conduction occurs through capillary action.

Hence a thin film of water is required on land, for survival.

• Yes, heterospory has evolutionary significance in plants.

• Heterospory led to in situ embryo development. The embryo derives nutrition from the female gametophyte and hence are better protected.

• Heterospory led to the evolution of seed habit, which helped the plants to flourish and tide over long periods of unfavourable conditions.

Due to the following reasons Lycopodium and Selaginella fall short of seed habit:

• Embryo was retained within the female gametophyte upto the development of rhizophore, roots and leaves only. Hence,there is no complete retention of embryo.

• The seeds of Selaginella and Lycopodium failed to develop protective covering called the integument.

• Cycas is the connecting link between Gymnosperms and Pteridophyte.

• It is placed under the division gymnosperm but due to following characters it resembles fern(pteridophyte):

a) It produces motile flagellated male gamete which resembles pteridophytes.

b) Armour of persistent leaf bases covers the columnar stem.

c) In Cycas revolute, marginal sori are present which resembles the coenosorus of Pteris.

d) Presence of bicelled hair called ramenta. Rachis of Pteris contains ramenta.

Following are the character which are assumed to be precursors of seed habit & helped it in the evolution.

i) Evolutionary heterospory

ii) In-situ development of embryo within the female gametophyte.

iii) Decrease in number of megaspore to one.

iv) Apex of megasporangium modified for reception of pollen.

v) Megasporium got enveloped by integements.

Life Cycle:

• Fern shows diplo-haplontic life cycle.

• Diploid sporophyte represents the dominant, independent, photosynthetic plant body.

• The sporophyte bears sporangia which produces spores by meiosis.

• These spores germinate to form free living prothallus which represents a gametophyte.

• Sexual reproduction: syngamy results in formation of diploid zygote. Zygote germinates into a diploid sporophyte.

Prothallus:

• It represents the gametophytic phase.

• Multicellular, independent, green, photosynthetic thallus.

• It needs damp and shady places.

• Bears sex organs, rhizoids and food laden parenchymatous cells.

• Mycorrhiza can be seen in Pinus and corolloid root in Cycas.

• Mycorrhiza – system association between the roots of higher plants & fungi. Fungi helps the plants in absorption of nutrients especially phosphorus in return it go to shelter.

Corolloid roots – when the roots of higher plants like Cycas shows association with BGA. It is also an example of symbiotic association

• Bryophyte shows haplodiplontic life cycle due to alternation between gametophytic and sporophytic phase of life.

• In bryophytes major part of the life cycle is dominated by haploid gametophytic phase.

• Gametophyte is independent, photosynthetic and haploid phase.

• Antheridium and archegonia are formed in gametophyte.

• Fertilization occurs, zygote is formed.

• Zygote developed into sporophytes which is small & is dependent on gametophyte for water and food.

Alternation of generation takes place between gametophyte & sporophyte. i.e. the haploid & diploid phase, hence called haplodiplontic life cycle.

b) Both will die

In the symbiotic relationship between algae & fungi, both are dependent on each other for their basic needs essential for survival.

Algal part synthesise food for fungi & fungi takes up water & minerals for algae.

If separated, both will die.

The polar cell contains 2 nuclei.

Double fertilization:

• It is the phenomenon in which when a pollen reaches the stigma of the female flower, it germinates to produce 2 male nuclei and a vegetative cell.

• The 2 male nuclei enters the embryo sac, one of the male gamete fuses with egg to form a diploid zygote & the other male gamete fuses with diploid secondary nucleus to form triploid primary endosperm nucleus (PEN).

• Hence, because of the two fusions this phenomenon is called double fertilization.

a.

b.

c.